// d2mcpp: https://github.com/mcpp-community/d2mcpp

// license: Apache-2.0

// file: src/en/cpp14/tests/00-generic-lambdas/1.cpp

//

// Exercise: cpp14 | 00 - generic lambdas | generic lambda with STL algorithms

//

// Tips:

// - A single generic lambda can be reused with containers of different

// element types

// - Captured variables retain their concrete types; only parameters use auto

//

// Docs:

// - https://en.cppreference.com/w/cpp/language/lambda

// - https://github.com/mcpp-community/d2mcpp/blob/main/book/en/src/cpp14/00-generic-lambdas.md

//

// Discussion Forum: http://forum.d2learn.org/category/20

//

// Auto-Checker:

//

// d2x checker generic-lambdas

//

import std;

import d2x;

int main() {

// 0. Same generic lambda used to sort containers of different element types

std::vector<int> v1 = {5, 1, 4, 2, 8};

std::vector<double> v2 = {3.1, 2.7, 8.5, 1.9};

auto desc = [](D2X_YOUR_ANSWER a, D2X_YOUR_ANSWER b) {

return a > b;

};

std::sort(v1.begin(), v1.end(), desc);

d2x::check_eq(v1[0], 8, "v1[0] == 8");

d2x::check_eq(v1[4], 1, "v1[4] == 1");

std::sort(v2.begin(), v2.end(), desc);

d2x::check_eq(v2[0], D2X_YOUR_ANSWER, "v2[0] == D2X_YOUR_ANSWER");

// 1. Generic lambda with capture — find_if

int threshold = 3;

auto above = [threshold](auto x) {

return x > threshold;

};

auto it1 = std::find_if(v1.begin(), v1.end(), above);

d2x::check(*it1 == D2X_YOUR_ANSWER, "*it1 == D2X_YOUR_ANSWER");

auto it2 = std::find_if(v2.begin(), v2.end(), above);

d2x::check(*it2 == 8.5, "*it2 == 8.5");

// 2. Generic lambda returning lambda — factory function

auto make_multiplier = [](auto factor) {

return [factor](auto x) { return x * D2X_YOUR_ANSWER; };

};

auto times2 = make_multiplier(2);

d2x::check_eq(times2(10), 20, "times2(10) == 20");

d2x::check_eq(times2(0.5), 1.0, "times2(0.5) == 1.0");

d2x::wait();

return 0;

}